1. Field of the Invention
This invention relates to semiconductor integrated power devices and means for controlling the minority carrier lifetime therein and for providing regions of current isolation between mutually adjacent devices.
2. Description of the Prior Art
Often two or more semiconductor power devices are manufactured on a common substrate to provide an integrated power device. Such an integrated power device may comprise a triac, which is two semiconductor controlled rectifiers in an antiparallel circuit arrangement, a reverse conducting semiconductor controlled rectifier, which is a semiconductor controlled rectifier and a rectifier in an antiparallel circuit arrangement, and transistor -- semiconductor controlled rectifier combinations. The manufacture and utilization of such device combinations on a common substrate necessitates satisfactory current isolation between adjacent power devices. Current isolation between devices is required to prevent injected carriers from a device which is in an "on" state from diffusing into neighboring devices and affecting the performance thereof.
Heretofore, current isolation has been achieved by the diffusing of gold metal into desired regions of a substrate. However, this process which is practiced has a serious disadvantage in that while gold is diffusing into the substrate to form the current isolation region, the gold is also diffusing into the active regions of the mutually adjacent devices as well. The end result of this extraneous gold diffusion is an adverse affect on the conductive losses and high temperature dv/dt of the power devices. A greater physical separation can be provided between mutually adjacent power devices but at the expense of the active volume of the substrate available for device fabrication.
An object of this invention is to provide a new and improved current isolation means between two mutually adjacent semiconductor devices in an integrated circuit which overcome the deficiencies of the prior art.
Another object of this invention is to provide current isolation means between mutually adjacent semiconductor devices in an integrated semiconductor device while requiring the employment of a minimum volume of semiconductor material.
A further object of this invention is to provide a means for controlling the minority carrier lifetime of one or more devices and simultaneously provide a current isolation region between the at least one device and a mutually adjacent semiconductor device.
Other objects of this invention will, in part, be obvious and will, in part, appear hereinafter.
In accordance with the teachings of this invention, there is provided a body of semiconductor material having two major opposed surfaces forming specifically the top and bottom surfaces of the body. The body also has a peripheral side surface and a first level of minority carrier lifetime. At least one region of recrystallized semiconductor material is disposed within the body substantially perpendicular to and extending between, and terminating in the two opposed major surfaces. The recrystallized semiconductor material has a metal disposed throughout the region to impart a second level minority carrier lifetime thereto. The at least one region has a substantially constant level of minority carrier lifetime throughout the region and divides the body into at least two mutually adjacent regions each of which is in abutting contact with the at least one region of recrystallized semiconductor material. A minority carrier lifetime junction is formed by the abutting surfaces of each pair of regions of different levels of minority carrier lifetime. A semiconductor device is formed in each of the at least two regions of the divided body. Suitable solid solubility materials include gold, platinum, silver, nickel and copper. Additionally, an array of recrystallized regions may provide a selected volume of at least one of the devices in order to control the minority carrier lifetime therein.